Created
August 29, 2011 08:13
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# the 2-dimensional convolution function | |
FloydConvolution <- function(a){ | |
c <- matrix(0, nrow=dim(a)[1], ncol=dim(a)[2]) | |
for(i in 1:(dim(a)[1]-1)){ | |
for(j in 1:(dim(a)[2]-1)){ | |
P <- trunc(a[i,j]+0.5) | |
e <- a[i,j] - P | |
a[i,j] <- P | |
a[i,j+1] <- a[i,j+1] + (e * 7/16) | |
a[i+1,j-1] <- a[i+1,j-1] + (e * 3/16) | |
a[i+1,j] <- a[i+1,j] + (e * 5/16) | |
a[i+1,j+1] <- a[i+1,j+1] + (e * 1/16) | |
} | |
} | |
a | |
} | |
# the main function | |
grey2FSdith <- function(img){ | |
greyMatrix <- img[1:nrow(img),1:ncol(img)] | |
dim1 <- 1 | |
dim2 <- 1 | |
dim1x <- 1 | |
dim2x <- 1 | |
dim1a <- dim(greyMatrix)[1] | |
dim2a <- dim(greyMatrix)[2] | |
# this code creates a bigger matrix (image) adding 0.5 values in first/last row/col | |
tempMatrix <- matrix(0.5, nrow=nrow(greyMatrix)+2, ncol=ncol(greyMatrix)+2) | |
tempMatrix[2:(nrow(tempMatrix)-1),2:(ncol(tempMatrix)-1)] <- greyMatrix | |
# apply the convolution function | |
igrey <- FloydConvolution(tempMatrix) | |
# create the image | |
imagematrix(igrey[1:(nrow(igrey)-1),1:(ncol(igrey)-1)], type="grey", noclipping=TRUE) | |
} | |
# plot the dithered imageg | |
plot(normalize(grey2FSdith(rgb2grey(y)))) |
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